Grapegrowers keep eye out for cold damage in vineyards as freezing conditions persist

San Rafael, Calif.—With low temperatures reaching the mid-teens to single digits across most of the western United States, growers are monitoring their vineyards for any signs of cold damage.

Across Washington, Oregon and in parts of Northern California, clear skies and little precipitation along with a persistent influx of cold, Arctic air have sent temperatures plummeting. According to the weather forecasting service AccuWeather, Dundee, Ore., saw a low of 9° F on Sunday, with similar lows in other parts of the state.

In Walla Walla, Wash., the weekend lows reached 3° F. Across much of California, temperatures hit the low teens or single digits.

Temperatures are forecast to rise back to normal levels this week, but in Washington growers are still monitoring the situation.

Jason Schlagel is the director of viticulture for Milbrandt Vineyards in Matawa, Wash. He said that temperatures reached a low of 1° F on Sunday. “We are probably still free of bud damage, but my staff will be taking some cuttings to evaluate buds as a precaution.”

When Schlagel was speaking to Wines & Vines at around 11 a.m. Monday, he noted the temperature had only reached 18° F. He said he’s been checking temperatures and vines regularly as conditions have remained frigid. The last time he recalled Washington experiencing a prolonged stretch of such cold weather was in 2010. “We get weather like this every five to three years,” he said.

Real-time cold hardiness
Washington State University posts “real-time” cold-hardiness data online. The most current report puts bud damage for Merlot at -5°, Syrah at -3.5° and Cabernet Sauvignon at -6.5° F. These temperatures would likely kill 10% of the primary buds. WSU currently estimates bark damage to begin for most of the major varieties if temperatures drop below 7° F.

Schlagel said it could take just an hour of such temperatures for the vines to suffer damage.

In Walla Walla, Marty Clubb the owner and managing winemaker of L’Ecole No 41 winery, said everybody in the region has been talking about the cold weather, but he was optimistic it shouldn’t be a problem. “I think, and hope, we are fine,” he said.

Based on the data from WSU, Clubb said he’s pretty sure his vines haven’t been damaged and likely won’t be. A relatively early end to the harvest—as well as some cold weather prior to the extended bout of freezing temps—helped push the vines into dormancy. “We’ve had more weeks to get dormant, but we’ve had some cold spells to get us even further into dormancy,” he said.

Still, Clubb said he’s been turning on fans for further protection against cold damage. “We are pretty gung-ho about turning the fans on,” he said.

Water still a bigger worry
While temperatures fell to less than 10° F in some parts of California’s North Coast, the freezing weather likely wouldn’t cause any serious vineyard damage.

“As for the effect of these cold temperatures on grapevines, we are not too worried,” said Jon Ruel, the president of the Napa Valley Grapegrowers and president of Trefethen Family Vineyards. “All the vines around here (Napa Valley) have entered dormancy and should already be hardy to at least 10° to 15° F.”

Ruel said he is more concerned about the lack of any significant rainfall to recharge the region’s aquifer and help ensure good conditions for the next vintage. “We actually sow cover crop by seed between our vine rows—including barley, rye, legumes—and the lack of fall rainfall has meant little to no germination,” he said. “The seeds may get moisture later, but then soil temp will be so low as to discourage good growth.”

Garrett Buckland, a partner with Premier Viticultural Services and a member of the Grapegrowers board, said it’s not unheard of to see bud damage from cold temperatures, but this is more from the buds drying out rather than physical damage from actually freezing. “With the record dry year and abnormally dry fall, growers are more at risk for bud damage, especially those that were unable to water post-harvest or those that did not see their vines shut down normally.”

He said the risk of damaged vineyard infrastructure such as pipes, irrigation sprinklers and valves is still pretty high as well.

Much further north in British Columbia, growers there were thankful that freezing temperatures provided an opportunity to harvest frozen grapes for ice wine. Beginning in late November, several wineries have harvested grapes for ice wine with the total haul expected to be around 1,000 tons.

Summerhill Pyramid Winery vineyard manager Willem Semmelink said in a statement that after a challenging summer he was happy the region saw a pleasant autumn and cold temperatures to ensure ice wine production. “We are pleased that the arctic express has arrived so early, allowing us to capture this amazing fruit so early in the season and avoid damage to nature’s gift.”